There are many commands which need to access data relevant to Uniform Resource Identifiers (URI). Each one needs to interface with a library or command line utility. Some examples of individual file systems include ftpfs, httpfs, sshfs, and nfs. However none of these individual file systems generically handle URIs. Most individual file systems are limited. For example, httpfs can only be used to access a single URL on a http 1.1 server.
Often times these interfaces limit access to data. For example, if a script is using wget to access content on the web, there is no good way to seek through the data in real time.